1. Field of the Invention
Embodiments of the present invention generally relate to the fabrication of integrated circuits. More particularly, the embodiments relates to methods for depositing dielectric layers on a substrate and structures that include the dielectric layer.
2. Description of the Related Art
Semiconductor device geometries have dramatically decreased in size since such devices were first introduced several decades ago. Since then, integrated circuits have generally followed the two year/half-size rule (often called Moore's Law), which means that the number of devices that will fit on a chip doubles every two years. Today's fabrication plants are routinely producing devices having 0.13 μm and even 0.1 μm feature sizes, and tomorrow's plants soon will be producing devices having even smaller geometries.
In order to further reduce the size of devices on integrated circuits, it has become necessary to use conductive materials having low resistivity and to use insulators having low dielectric constants (k) to reduce the capacitive coupling between adjacent metal lines. One such low k material is spin-on glass, such as un-doped silicon glass (USG) or fluorine-doped silicon glass (FSG), which can be deposited as a gap fill layer in a semiconductor manufacturing process. Other examples of low k materials include carbon doped silicon oxides and polytetrafluoroethylene. However, the continued reduction in device geometries has generated a demand for films having even lower k values.
Recent developments in low dielectric constants have focused on incorporating silicon, carbon, and oxygen atoms into the deposited film. One of the approaches to obtain an ultra low dielectric constant is to fabricate hybrid films of an organic porogen and a silicon matrix. During the post-treatment, the porogens are removed, resulting in porous low k materials. These porous films are known to have less adhesion to underlying barrier layers than silicon oxides. Improvement of adhesion may be obtained by depositing an initiation layer of oxide, which can enhance adhesion at the interface. To further improve adhesion, it has been suggested to use a gradient layer with increasing carbon content gradually between initiation and main deposition step. However, this method can cause undesirable gas phase reaction causing unwanted particles to form in the films, resulting in defect issues. Therefore, there is a need for a process for making low dielectric constant materials with improved adhesion and without particle defect issues.